* Editor's note: This is Part 2 of a two-part answer to the following question (Part 1 ran Dec. 5):

Dear Colin: I have osteoporosis that's worse in my hips. To help increase my bone density, I hike trails at a nature park, usually with a weighted vest, but stopped when my knees started hurting. Are there exercises that would increase my hip bone density without risking fracture and hurting my knees? -- Bonnie, Portland

While there are potentially effective exercises that can yield remarkable benefits, they must be done correctly to minimize risk of injury to the knee and other joints.

If you're new to strengthening, try this exercise near your kitchen counter so you can lightly touch it with one hand for balance. Even if you're an experienced exerciser, work on getting the technique right before adding dumbbells.

In the starting position, your front knee is slightly bent, your back heel off the ground. You should focus on tensing your front thigh and "relaxing" your back thigh so that little pressure is felt through the back foot. This takes mental skill and time to develop.

Safe starting position for the knee. Ty Downing

In the end point for the down phase, you should be bending the front knee about 50-60 degrees while dropping the back knee toward the floor. You should lean forward slightly, keep your hips back, pelvis completely level and knee in line with the toes. Allowing your knee to collapse inward decreases demand on working muscles and is potentially damaging to the knee, hip and ankle; keep the knee straight the entire time.

At the end point for the up phase, focus on tensing the front leg and relaxing the back leg. "Sharing" your weight equally between both legs will make this exercise far too easy, prompting you to use heavier weight than necessary. Consequently, there's an increased risk of back, shoulder, hip and knee injury.

To minimize exercise time, do the lunge in the manner shown in two of the accompanying photos and perform 15-20 repetitions on one leg, then switch to the other.

Safe ending knee position for stationary lunge Ty Downing

Another version is the walking lunge, where you alternate one leg with the other in a walking fashion, which allows muscles to rest between repetitions (which is counterproductive, though, if time is important to you). As a general rule in resistance training, try to maintain tension on working muscles to minimize exercise time while maximizing benefit. Colin Hoobler is hosting a charity event, "Overcoming Knee Pain," 9-11 a.m. Jan. 26 at Portland State's Stott Center. To register, visit chpt.org.